Determination of glycerol in wine - comparison and validation of existing methods

Project details

Total cost:

EU contribution:

Coordinated in:

Topic(s):

Funding scheme:

CSC - Cost-sharing contracts

Objective

In the EU, wine production makes a considerable contribution to the value of final agricultural output and is an important part of the EU's economy. However, competition is increasing with third country imports, some of which are not produced to the same stringent standards as the home products. Glycerol is a natural constituent of the wine and since it is a quality-determining parameter, it may be deliberately added to poor quality wines.

This project proposes to address this problem by producing a validated methodology for the detection of glycerol in wine based on traditional GC-MS method for detecting the by-products of glycerol production and on stable isotopic analysis, used to identify the natural or synthetic source of the glycerol. The final output will consist of clear, precise experimental protocols and guidelines for implementing the methods and for interpreting the results. This know-how will be transferred to the main official user laboratories during a training workshop.The project has produced two literature surveys - one on existing analytical methods for glycerol detection and the other on the biosynthesis and technical production of glycerol. From the development work carried out in the preliminary stages of the project, two of the methods were formally validated. The GC-MS method of glycerol by-products has been completely validated. It was demonstrated that the concentrations of 3-MPD and cyclic diglycerides in different wines can be determined accurately and precisely enough in different laboratories. The stable isotope analysis of glycerol using GC-IRMS was also collaboratively studied. There were fewer participants in this case because of the specialised equipment required. Depending on the origin of the non wine glycerol, this method can be used to detect its addition in wine. The other isotopic analyses focused on the determination of deuterium/hydrogen ratios of the glycerol either by NMR or by IRMS.

The results will be published in a scientific paper. The use of oxygen-18/oxygen-16 ratio analyses was also investigated. This involved overcoming a number of technical problems, in particular the handling of glycerol before and during the analysis, as well as the instrumental conditions (pyrolysis conditions to improve the repeatability and even the "comparability" of the results). Although it did not reach validation stage, the work carried out has provided a significant step forward in using this method for future fraud detection. A data base of both isotopic values and impurity data (concentrations of CycD and 3-MPD) has been compiled for commercially-available and natural sources of glycerol has also been compiled.